Day/night sights would typically be used by military and law enforcement personnel to aim weapons used in both day time and night time conditions. Typically, a day/night sight includes an objective lens, a reticle and an eyepiece in series with parallel day and night channels. A channel selector may be used to alternatively direct an image of a target into the day or night channel.
In a day/night sight, the objective lens and the eyepiece may be telescopic to provide a magnified image of the target. The day channel generally uses ambient light to generate an image of the target. The image may be projected to the reticle during day time use to be viewed by the user. The night channel generally includes an image intensifier to generate an illuminated image of the target. The illuminated image may be transmitted to the reticle during night time use to be viewed by the user. The reticle may include markings for aiming the weapon.
Day/night sights suffer from numerous disadvantages, mainly attributable to problems aligning image beams from the separate day and night channels. Often, image beams from the day and night channels are projected onto different locations of the reticle. For example, the image beam of the day channel may be projected above and to the left of a reticle center while the image beam of the night channel may be projected below and to the right of the reticle center. Consequently, the reticle cannot be positioned to where it is centered, and thus accurate, for both channels.